Now for me, this is where it gets interesting, because even though you haveselected the customized grid file, it will not use this customized file inthe calculations, even though it say its using it in the header of the outputfile!

Here's where I exit the program and then start it up again...try it.

One way to insure that the correct model is being used, would be to visit theNGS website (they only run the old model), and run a point through theironline version of the VertCon program thereby getting a second opinion:http://www.ngs.noaa.gov/TOOLS/Vertcon/vertcon.html Click "Height Conversion"on the left side. If you run a coordinate here, say 27 00 00.00 and 081 1200.00, you will get a datum difference of -0.353 meters (-1.158 ft). Thenrun this same position through CorpsCon, and see if you get this number or adifferent conversion. I know this is not to most comforting nor scientificsystem, but the other option is to wait until the next version of Corpscon isreleased...December 21, 2012.

If you want to never have to think about this again, you could go toC:\Program Files\Corpscon6\Vertcon on your hard drive, and rename the filevertcone.94 to vertcone.94.old, and then rename vertcone.05 tovertcone.94...that way the software will have no choice but to use the newmodel file. I like to have both though, you you'll probably want to keepthat option.

Aside for a few select locations, I never really took a close look at thedifference between the two VertCon models....

I made a grid based roughly on the center of each of the 7.5min USGS Quadmaps for the eastern part of Florida. I then ran two sessions of CorpsCon,first using the old, original 1994 Vertcon, then the 2005 CERP GeodeticControl Network supported model. Each time, I used as an NGVD29 elevation of0.00', and calculated the NAVD88 conversion. I then took the differencebetween these two iterations and generated the surface model shown in theattached files.

The file "Vertcon-Comparison.pdf" shows the difference between the resultsthat would be reached by using each of the two vertcon models. The range is+0.15' west of Lake Okeechobee to -0.06' in Palm Beach county. Again, thisis the difference between the results obtained by each model. As an examplesee file "VertCon-Comparison-Lake.pdf". At each data point are two textannotations, the one in blue is the result from the original NOAA/NGS Vertconmodel, and the Red is from the USACE generated CERP-VertCon. One of the datapoints in this file just at the west side of the lake has a red number of-1.33, and a blue number of -1.18. What this means, is that for a publishedNGVD29 elevation of 10.00', the original vertcon would return an NAVD88 of8.82', while the new model would result in 8.67'...that's the 0.15'difference.